Technical Abstract:
This research studied different juicing methods resulting in commercially processed and fresh squeezed juice with or without pasteurization for effect on level of nutrients and phytonutrinets in ‘Valencia’ and ‘Hamlin’ orange juices. Commercial processing included use of a juice extractor, finisher, and thermo pasteurizer. The juice extractor longitudinally cut fruit and made multiple wounds and then pressed the fruit to obtain juice. The extractor system is equipped with a mechanism to separate peel oil from the juice, resulting in about 0.015-0.025% oil in the subsequent processed samples. On the other hand, the juicer used for fresh squeezed samples is a combination of fruit half-cutters and automatic self-reversing reamers. There was more peel oil (0.9-1.5%) and less albedo/membrane tissues in fresh squeezed juice than in the commercially processed juice. Fresh squeezed juice, regardless pasteurization, had >4- and 8-fold higher levels of peel oil than processed juice in ‘Hamlin’ and ‘Valencia’, respectively. However, commercially processed juice had higher levels of particulates and solids (pectin and fiber). Total sugar contents were similar in all samples, expressed as Brix, however, commercially processed juice had higher contents of citric, malic and ascorbic acids, followed by fresh squeezed and then fresh squeezed with pasteurization. The majority of water soluble flavonoids including hesperidin, narirutin, narirutin 4'-glucoside, 6,8-di-C-glucosyl apigenin and isosakuranetin rutinoside, exhibited higher levels in commercially processed juice. On the other hand, flavonoids associated with peel oil, such as quercetagetin hexamethyl ether, sinensetin, nobiletin, tetramethyl-scutellarein, heptamethoxyflavone and tangeretin, had much higher concentrations in fresh squeezed juice because of the high oil content. Upon centrifugation, commercially processed juice had generally higher limonoids and alkaloids in the supernatant (juice serum), while the pellet had lower limonin glucoside. Commercially processed juice also had the highest total phenolic content. Thus, fresh squeezed juice had higher peel oil and associated oil-soluble flavonoids, however, commercially processed juice had higher levels of pectin and solids, water-soluble flavonoids, limonoids, alkaloids, phenolic content, organic acids and ascorbic acid. Pasteurization of fresh squeezed juice caused a slight decrease in the organic acids, but did not influence levels of other compounds.